Conventional doors are supported on the door jam by a plurality of hinge sets allowing the door to pivot from a closed position to an open position. For providing a locked condition, simple locking mechanisms are incorporated in the door handle assembly. Such locks are relatively easy to defeat with simple tools, and accordingly supplemental dead bolt locks are often used for additional protection against unauthorized entrance. In addition to time and expense for installation, the same are also aesthetically unattractive.
Various hinge based devices have been proposed for providing a locking capability directly at the hinges. These approaches has generally been directed to convenience and deterrence rather than security against unwanted intrusion.
U.S. Pat. No. 1,683,814 to Block patent discloses a hinge assembly wherein a circular hinge pin having a radial tab engages a radial slot on the hinge knuckle to prevent opening or limit opening of a door. The assembly is primarily intended for use in low force applications such as limiting door movement to prevent damage to adjacent furniture and doors, acting primarily as an alternative to a door stop. The tab is relatively thin and provides limited shear resistance to the large torques applied in forceful entry.
U.S. Pat. No. 5,642,910 to Betherum discloses a hinge lock that slides over the hinge assembly and captures the hinge plates at slots to prevent movement of the door from a selected position. The design also would be subject to shear and deformation at high force levels.
U.S. Pat. No. 6,591,453 to Jenks discloses a locking hinge system wherein a separate, small diameter pin is inserted into a vertically aligned series of holes outwardly of the hinge pin to lock the hinge plates at open or closed positions. These device is a very light weight construction having small shear interfaces resisting unwanted movement.